Facilitating efferent inhibition of inner hair cells in the cochlea of the neonatal rat
Facilitating efferent inhibition of inner hair cells in the cochlea of the neonatal rat
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DOI：
10.1113/jphysiol.2005.087460
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发表时间：
2005-07-01
影响因子：
5.5
通讯作者：
Glowatzki, E
中科院分区：
文献类型：
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作者：
Goutman, JD;Fuchs, PA;Glowatzki, E
胆碱能脑干神经元在成熟哺乳动物耳蜗的外毛细胞（OHC）和听力开始前的内毛细胞（IHC）上形成抑制性突触。我们使用的Corti准备的切除器官的电刺激检查诱发释放乙酰胆碱（ACh）到新生儿的IHC从这些传出纤维。全细胞电压钳记录显示，低频（0.25-1Hz）电刺激产生的诱发抑制性突触后电流（IPSC）在相对高的失败率（65%）下，在-90mV下的平均幅度约为-20pA，对应于类似于1的量子含量。诱发的IPSC在-60 mV下具有双相波形，被α-银环蛇毒素和士的宁可逆地阻断，并且最可能由α 9/α 10乙酰胆碱受体介导，随后激活钙依赖性钾（SK 2）通道。间隔为10- 100 ms的成对脉冲刺激使IPSC的平均振幅易化200-300%。由于整个脉冲串的易化和求和，具有25 ms脉冲间间隔的10个脉冲的脉冲串产生越来越大的IPSC，最大振幅大于-100pA。5 Hz或更高频率的重复传出刺激可使IHC超极化5- 10 mV，并可完全阻止去极化电流诱发的钙动作电位的产生。
Cholinergic brainstem neurones make inhibitory synapses on outer hair cells (OHCs) in the mature mammalian cochlea and on inner hair cells (IHCs) prior to the onset of hearing. We used electrical stimulation in an excised organ of Corti preparation to examine evoked release of acetylcholine (ACh) onto neonatal IHCs from these efferent fibres. Whole-cell voltage-clamp recording revealed that low frequency (0.25-1Hz) electrical stimulation produced evoked inhibitory postsynaptic currents (IPSCs) at a relatively high fraction of failures (65%) and with mean amplitudes of about -20pA at -90mV, corresponding to a quantum content of similar to 1. Evoked IPSCs had biphasic waveforms at -60mV, were blocked reversibly by alpha-bungarotoxin and strychnine and are most likely mediated by the alpha 9/alpha 10 acetylcholine receptor, with subsequent activation of calcium-dependent potassium (SK2) channels. Paired pulse stimulation with intervals of 10-100ms caused facilitation of 200-300% in the mean IPSC amplitude. A train of 10 pulses with an interpulse interval of 25ms produced increasingly larger IPSCs with maximum amplitudes greater than -100pA due to facilitation and summation throughout the train. Repetitive efferent stimulation at 5Hz or higher hyperpolarized IHCs by 5-10mV and could completely prevent the generation of calcium action potentials normally evoked by depolarizing current injection.